When the eyes execute a rapid fixation change (a saccade), no movement of the visual environment is perceived although visual images are swept across the retina. Many investigators have attributed the decrease in visual sensitivity during saccades to an oculomotor "corollary discharge" which suppresses vision before and during the movement. Preliminary psychophysical studies in our lab, on the other hand, show that the consequences for vision are the same whether the eye itself moves, or the visual background is displaced with comparable amplitude and velocity. The objective of the research in this application is to determine the coding of incoming visual information by single units of the primate visual system during eye movements. To this end we propose two parallel projects. One concerns the psychophysics of vision during eye movement in humans and is a continuation of work in progress. Subjects will be required to make eye movements across a variety of backgrounds while test stimuli ranging from small spots to full field flashes are presented before, during and after the movement; the effect of eye movements on visual sensitivity will be compared with the effect of comparable movements of the background. The other is a coordinated neurophysiological investigation of single unit activity both in the visual system of monkeys trained to eye movements, and in acute, anesthetized monkeys with immobilized eyes.